This invention relates to the recovery of gasoline vapors from gasoline dispenser systems.
As smog conditions have gone from bad to worse in larger cities, every effort has been made to reduce the amount of hydrocarbons released into the atmosphere from all sources. One relatively large source of atmospheric hydrocarbons is gasoline vapors being expelled from the gasoline tanks of automobiles when they are being refueled. Before being refueled, the nearly empty gasoline tank is filled with gasoline vapor. As gasoline is pumped into the empty gasoline tank, the gasoline vapor is pushed out of the tank and into the atmosphere through the clearance between the refueling nozzle and the gasoline inlet opening. Gasoline vapor released into the atmosphere in this manner can amount to 15% of the total hydrocarbons released from the tailpipes of automobiles and trucks. Therefore, in recent years, efforts have been made to develop vapor recovery systems for preventing the gasoline vapors from being released into the atmosphere during refueling.
Basically, these systems involve creating a vapor seal over the gasoline inlet opening when the refueling nozzle is inserted therein and providing a vapor recovering conduit which extends from the nozzle to the gasoline underground storage tank so that the gasoline vapors are pushed or drawn into the storage tank during the refueling instead of being released into the atmosphere.
There are two different types of vapor recovery systems: The balanced system and the vacuum-assist system. The balanced system relies on the push exerted by gasoline entering the gasoline tank and displacing the gasoline vapor which had previously filled with tank. This push is sufficient to move the vapors down the vapor recovery conduit into the underground gasoline storage tank. Since the volume of vapor displaced by gasoline entering the gasoline tank is equal to the volume left vacant by gasoline leaving the storage tank, there is always room in the storage tank for the displaced vapor.
The vacuum-assist system uses a vacuum or other assist means to draw the gasoline vapors into the underground storage tank. The balanced system requires a relatively tight vapor seal at the gasoline inlet opening to prevent any vapor from escaping into the atmosphere. The vacuum-assist system does not require such a tight vapor seal. Since a tight vapor seal is difficult to obtain on some cars, the balanced system is not as efficient as the vacuum-assist system. There are many small stations, however, where the efficiency of a vacuum-assist system is not required.
This invention relates to balanced vapor recovery systems. The problem with presently available balanced systems is that they use a complex heavy nozzle that is hard to handle. It is complex and heavy because it performs several functions. It not only collects vapors, but also opens the vapor conduit before use and closes it after use, and has an interlock to prevent dispensing gasoline unless a good fit is achieved. These functions are necessary in order to force the customer to operate the nozzle properly, to prevent vapors from leaking back out from the underground tank, and to prevent any accidental flame from propagating down the vapor recovery conduit to the underground storage tank.